Generally a hearing aid system according to the invention is understood as meaning any system which provides an output signal that can be perceived as an acoustic signal by a user or contributes to providing such an output signal, and which has means which are used to compensate for an individual hearing deficiency of the user or contribute to compensating for the hearing deficiency of the user. These systems may comprise hearing aids which can be worn on the body or on the head, in particular on or in the ear, and can be fully or partially implanted. However, some devices whose main aim is not to compensate for a hearing deficiency may also be regarded as hearing aid systems, for example consumer electronic devices (televisions, hi-fi systems, mobile phones, MP3 players etc.) provided they have, however, measures for compensating for an individual hearing deficiency.
Within the present context a hearing aid may be understood as a small, battery-powered, microelectronic device designed to be worn behind or in the human ear by a hearing-impaired user.
Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, resulting in a so-called audiogram, of the performance of the hearing-impaired user's unaided hearing. The prescription may be developed to reach a setting where the hearing aid will alleviate a hearing deficiency by amplifying sound at frequencies in those parts of the audible frequency range where the user suffers a hearing deficit.
A hearing aid comprises one or more microphones, a battery, a microelectronic circuit comprising a signal processor, and an acoustic output transducer. The signal processor is preferably a digital signal processor. The hearing aid is enclosed in a casing suitable for fitting behind or in a human ear. For this type of traditional hearing aids the mechanical design has developed into a number of general categories. As the name suggests, Behind-The-Ear (BTE) hearing aids are worn behind the ear. To be more precise, an electronics unit comprising a housing containing the major electronics parts thereof is worn behind the ear, and an earpiece for emitting sound to the hearing aid user is worn in the ear, e.g. in the concha or the ear canal. In a traditional BTE hearing aid, a sound tube is used to convey sound from the output transducer, which in hearing aid terminology is normally referred to as the receiver, located in the housing of the electronics unit and to the ear canal. In some modern types of hearing aids a conducting member comprising electrical conductors conveys an electric signal from the housing and to a receiver placed in the earpiece in the ear. Such hearing aids are commonly referred to as Receiver-In-The-Ear (RITE) hearing aids. In a specific type of RITE hearing aids the receiver is placed inside the ear canal. This category is sometimes referred to as Receiver-In-Canal (RIC) hearing aids. In-The-Ear (ITE) hearing aids are designed for arrangement in the ear, normally in the funnel-shaped outer part of the ear canal. In a specific type of ITE hearing aids the hearing aid is placed substantially inside the ear canal. This category is sometimes referred to as Completely-In-Canal (CIC) hearing aids. This type of hearing aid requires an especially compact design in order to allow it to be arranged in the ear canal, while accommodating the components necessary for operation of the hearing aid.
Within the present context a hearing aid system may comprise a single hearing aid (a so called monaural hearing aid system) or comprise two hearing aids, one for each ear of the hearing aid user (a so called binaural hearing aid system). Furthermore the hearing aid system may comprise an external device, such as a smart phone having software applications adapted to interact with other devices of the hearing aid system, or the external device alone may function as a hearing aid system. Thus within the present context the term “hearing aid system device” may denote a traditional hearing aid or an external device.
It is well known for persons skilled in the art of hearing aid systems that some hearing aid system users are not satisfied with the performance of conventional hearing-aid systems that primarily are configured to relieve the detrimental effects of suffering from an elevated hearing threshold.
One method of operating a hearing aid system that has proven beneficial for hearing aid system users diagnosed with an elevated hearing aid threshold is disclosed in e.g. EP-B1-1932389. Herein is disclosed a so called compressor that applies a frequency dependent gain as a function of input signal level and the degree of hearing loss. The compressor ensures that an appropriate gain is applied such that the elevated hearing threshold is compensated.
Another method of operating a hearing aid system that has proven beneficial for hearing aid system users diagnosed with an elevated hearing aid threshold is disclosed in EP-B1-1522206. This method is capable of optimizing speech intelligibility of an acoustical signal by applying a frequency dependent gain. The frequency dependent gain is determined iteratively. The method takes factors such as signal-to-noise ratio, masking effects and frequency band importance into account.
Yet another method of operating a hearing aid system that has proven beneficial for hearing aid system users diagnosed with an elevated hearing aid threshold is given in EP-B1-1380187 that discloses a directional system that is capable of suppressing noise from undesired directions.
A subgroup of potential hearing aid users are assumed to have auditory-nerve dysfunction (that may also be denoted auditory neurodegeneration) due to aging or ototoxic drug exposure or noise trauma. This type of hearing deficit is typically not diagnosed as part of a traditional hearing aid fitting and consequently few, if any, methods of operating hearing aid systems in order to relieve this type of hearing deficit are available.
It is therefore a feature of the present invention to suggest a method of operating a hearing aid system in order to provide hearing-aid sound processing that can benefit individuals with an auditory-nerve dysfunction.
It is another feature of the present invention to suggest a hearing aid system adapted to carry out a sound processing method that can benefit individuals with an auditory-nerve dysfunction.